This invention relates to a mower with two sickle bars.
Conventional mowers of the type for use for example with a combine or with a swather include a sickle bar which is movable transversely to a frame of the mower across a front edge thereof. The sickle bar carries a plurality of thin knife elements which are triangular in plan and which project forwardly from the sickle bar and slide over a trash bar and between slots defined in knife guards which project forwardly from the trash bar. Each knife guard defines a ledger surface having sharpened shearing edges for cooperating with the knife element and includes a knife element retaining plate parallel to and overlying the ledger surface so as to define the slot through which the knife element moves.
The amount of reciprocation of the sickle bar is of course sufficient move each knife element across the frame from a position within one knife guard to a position within the next adjacent knife guard. Thus each movement acts to create a cutting action between the knife element and the knife guard as it moves into the slot defined by the knife guard.
In many cases the mower element or frame is of limited width so that a single sickle bar can extend from one end to the other end and be driven at one of the ends for reciprocation back and forth.
In other cases, and particularly in more recent years as the width of such mower devices has increased, it has been found necessary to provide two such sickle bars extending inwardly from respective ends to a mid position. Such an arrangment including two sickle bars can reduce the forces involved on the drive mechanisms in comparison with the forces on a single sickle bar of double length. In addition, the two sickle bars can be driven in opposite phase so as to reduce vibration caused by the reciprocating mass.
However, a problem arises in an arrangement of this type in that the sickle bars and knife elements must be arranged to cooperate in some way at the mid position to properly cut the crop at that position while of course avoiding any mechanical contact between the sickle bars and moving elements. It will of course be appreciated that the cutting of the crop at the mid position must continue effectively normally otherwise plugging of the mower at this section can occur.
Various prior proposals have been made for overcoming this problem and perhaps the most simple is shown in U.S. Pat. No. 3,771,297 which shows a divider plate at the central section which is intended to direct the crop away of the central section.
Another arrangement is disclosed in U.S. Pat. No. 3,508,388 in which there is provided an extra wide ledger surface and effectively the knife elements at the inboard end of each sickle bar are formed by half elements so that the two bars effectively abut at the inward end of the stroke with the inboard cutting edge being defined by a straight for and aft edge in place of the conventional inclined side edge of the triangular knife elements.
A yet further type of arrangement is disclosed in U.S. Pat. Nos. 3,577,716 and 4,236,370 in which an extension piece is attached to one end of one of the sickle bars and extends over a gap between the inboard ends so as to provide a cutting effect in that gap. These arrangements are complicated and require a number of different knife elements thus complicating the replacement part situation.
A yet further design is used on designs manufactured by the Hesston Company in which the inboard ends are arranged so that one slides on the other with the knife elements at those ends being modified to provide a cutting effect. This again is a complicated arrangement using different knife elements and having a reduced or less effective cutting action at the center section.